Multilayer blown films for shrink applications

ABSTRACT

The present invention discloses multilayer blown films for shrink label and related applications. These multilayer blown films can comprise a core layer containing an ethylene polymer, and inner and outer layers containing conjugated diene monovinylarene block copolymers.

REFERENCE TO RELATED APPLICATION

This application is a divisional application of U.S. patent applicationSer. No. 13/106,008, filed on May 12, 2011, now U.S. Pat. No. 9,174,377the disclosure of which is incorporated herein by reference in itsentirety.

BACKGROUND OF THE INVENTION

The present invention relates generally to multilayer blown films withdesirable shrink characteristics. These multilayer blown films can beused in label applications, such as shrink sleeve labels and roll fedshrink labels.

SUMMARY OF THE INVENTION

This summary is provided to introduce a selection of concepts in asimplified form that are further described below in the detaileddescription. This summary is not intended to identify required oressential features of the claimed subject matter. Nor is this summaryintended to be used to limit the scope of the claimed subject matter.

Multilayer blown films disclosed and described herein can comprise threeor more layers, and can be characterized by various shrink properties,for example, a MD shrink of greater than about 60%, and/or a CD shrinkin a range from 0% to about 15%, and/or a MD:CD shrink ratio in a rangefrom about 4:1 to about 30:1. These multilayer blown films can beproduced using standard blown film processes, without any orientationprocesses involving tenter frame, double bubble, or machine directionorientation equipment.

For instance, an embodiment of this invention is directed to amultilayer blown film, and in this embodiment, the multilayer blown filmcan comprise (a) a core layer having a first side and a second side, (b)an inner layer positioned on the first side of the core layer, and (c)an outer layer positioned on the second side of the core layer. In thisembodiment, the multilayer blown film can have a MD:CD shrink ratio in arange from about 4:1 to about 30:1 at 150° C., and/or a MD shrink ofgreater than about 60%, and/or a CD shrink in a range from 0% to about15%.

Another embodiment of this invention also is directed to a multilayerblown film, and in this embodiment, the multilayer blown film cancomprise (a) a core layer having a first side and a second side, thecore layer comprising an ethylene polymer, (b) an inner layer positionedon the first side of the core layer, the inner layer comprising a firstconjugated diene monovinylarene block copolymer, and (c) an outer layerpositioned on the second side of the core layer, the outer layercomprising a second conjugated diene monovinylarene block copolymer.This multilayer blown film can have a MD:CD shrink ratio in a range fromabout 4:1 to about 30:1 at 150° C., and/or a MD shrink of greater thanabout 60%, and/or a CD shrink in a range from 0% to about 15%.Additionally, the ethylene polymer can have a MI in a range from about0.01 to about 2 g/10 min, a ratio of HLMI/MI in a range from about 50 toabout 300, and a ratio of Mw/Mn in a range from about 5 to about 30.

Embodiments of the invention also are directed to processes forproducing multilayer blown films. One such process can comprise (i)introducing into a blown film coextrusion die: (a) a core layer flowhaving a first side and a second side, the core layer flow comprising anethylene polymer, (b) an inner layer flow positioned on the first sideof the core layer flow, the inner layer flow comprising a firstconjugated diene monovinylarene block copolymer, and (c) an outer layerflow positioned on the second side of the core layer flow, the outerlayer flow comprising a second conjugated diene monovinylarene blockcopolymer; and (ii) blowing a coextruded flow exiting the die at ablow-up ratio in a range from about 1.5 to about 4 to produce themultilayer blown film.

Both the foregoing, summary and the following detailed descriptionprovide examples and are explanatory only. Accordingly, the foregoingsummary and the following detailed description should not be consideredto be restrictive. Further, features or variations may be provided inaddition to those set forth herein. For example, certain embodiments maybe directed to various feature combinations and sub-combinationsdescribed in the detailed description.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 presents an illustration of a 3-layer blown film structureaccording to an embodiment of the present invention.

FIG. 2 presents an illustration of a 4-layer blown film structureaccording to an embodiment of the present invention.

FIG. 3 presents an illustration of a 5-layer blown films structureaccording to an embodiment of the present invention.

FIG. 4 presents an illustration of a 7-layer blown film structureaccording to an embodiment of the present invention.

FIG. 5 presents a plot of the haze for the 3-layer blown films ofExamples 1-5.

FIG. 6 presents a plot of the 60° gloss for the 3-layer blown films ofExamples 1-5.

FIG. 7 presents a plot of the 1% secant modulus, in the machinedirection and cross (transverse) direction, for the 3-layer blown filmsof Examples 1-5.

FIG. 8 presents a plot of the percentage shrink, in the machinedirection and cross (transverse) direction, for the 3-layer blown filmsof Examples 1-5.

FIG. 9 presents a plot of the tensile strength at break, in the machinedirection and cross (transverse) direction, for the 3-layer blown filmsof Examples 1-5.

FIG. 10 presents a plot of the dart impact strength for the 3-layerblown films of Examples 1-5.

FIG. 11 presents a plot of the percentage shrink, in the machinedirection and cross (transverse) direction, for the 3-layer blown filmsof Examples 6-9 produced at a range of blow-up ratios.

DEFINITIONS

To define more clearly the terms used herein, the following definitionsare provided. Unless otherwise indicated, the following definitions areapplicable to this disclosure. If a term is used in this disclosure butis not specifically defined herein, the definition from the IUPACCompendium of Chemical Terminology, 2^(nd) Ed (1997) can be applied, aslong as that definition does not conflict with any other disclosure ordefinition applied herein, or render indefinite or non-enabled any claimto which that definition is applied. To the extent that any definitionor usage provided by any document incorporated herein by referenceconflicts with the definition or usage provided herein, the definitionor usage provided herein controls.

Regarding claim transitional terms or phrases, the transitional term“comprising,” which is synonymous with “including,” “containing,”“having,” or “characterized by,” is inclusive or open-ended and does notexclude additional, unrecited elements or method steps. The transitionalphrase “consisting of” excludes any element, step, or ingredient notspecified in the claim. The transitional phrase “consisting essentiallyof” limits the scope of a claim to the specified materials or steps andthose that do not materially affect the basic and novelcharacteristic(s) of the claimed invention. A “consisting essentiallyof” claim occupies a middle ground between closed claims that arewritten in a “consisting of” format and fully open claims that aredrafted in a “comprising” format. Absent an indication to the contrary,describing a compound or composition as “consisting essentially of” isnot to be construed as “comprising,” but is intended to describe therecited component that includes materials which do not significantlyalter the composition or method to which the term is applied. Forexample, a layer consisting essentially of a polymer includes impuritiesand additives typically present in a commercially produced orcommercially available sample of the recited polymer. Moreover, a layerconsisting essentially of a polymer also includes any combination ofadditives (or masterbatches) commonly used by producers of blown film incombination with the impurities and additives typically present in acommercially produced or commercially available sample of the recitedpolymer. When a claim includes different features and/or feature classes(for example, a method step, composition features, and/or propertyfeatures, among other possibilities), the transitional terms comprising,consisting essentially of, and consisting of apply only to the featureclass to which it is utilized, and it is possible to have differenttransitional terms or phrases utilized with different features within aclaim. For example, a method can comprise several recited steps (andother non-recited steps), but utilize a layer composition consisting ofa specific polymer and other components; alternatively, consistingessentially of a specific polymer and other components; oralternatively, comprising a specific polymer and other components andother non-recited components.

Therefore, while compositions and methods are described in terms of“comprising” various components or steps, the compositions and methodscan also “consist essentially of” or “consist of” the various componentsor steps, unless stated otherwise. For example, a core layer provided inan embodiment of the invention can comprise, or alternatively, consistessentially of or alternatively, consist of, an ethylene polymer.

The terms “a,” “an,” and “the” are intended to include pluralalternatives, e.g., at least one. For instance, the disclosure of “aconjugated diene monovinylarene block copolymer,” “an ethylene polymer,”etc., is meant to encompass one, or mixtures or combinations of morethan one conjugated diene monovinylarene block copolymer, ethylenepolymer, etc., unless otherwise specified.

The term “polymer” is used herein generically to include homopolymers,copolymers, terpolymers, and so forth. A copolymer is derived from amonomer and one comonomer, while a terpolymer is derived from a monomerand two comonomers. Accordingly, “polymer” encompasses copolymers,terpolymers, etc., derived from any monomer and comonomer(s) disclosedherein. Similarly, an ethylene polymer would include ethylenehomopolymers, ethylene copolymers, ethylene terpolymers, and the like.As an example, an ethylene polymer can be derived from ethylene and oneor more comonomers, such as 1-butene, 1-hexene, or 1-octene. If themonomer and comonomer were ethylene and 1-hexene, respectively, theresulting polymer would be categorized an as ethylene1-hexene copolymer.

In like manner, the scope of the term “polymerization” includeshomopolymerization, copolymerization, terpolymerization, etc. Therefore,a copolymerization process would involve contacting one olefin monomer(e.g., ethylene) and one olefin comonomer (e.g., 1-hexene) to produce acopolymer.

As used herein, a “conjugated diene” refers to an organic compoundcontaining conjugated carbon-carbon double bonds and a total of 4 to 12carbon atoms, such as 4 to 8 carbon atoms. Exemplary conjugated dienescan include, but are not limited to, 1,3-butadiene,2-methyl-1,3-butadiene, 2-ethyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, pentadiene, 3-butyl-1,3-octadiene, and mixturesthereof. For example, in some embodiments disclosed herein, theconjugated diene can be 1,3-butadiene. A unit of a polymer, wherein theunit is derived from polymerization of a conjugate diene monomer, is a“conjugated diene unit.”

As used herein, “monovinylarene” refers to an organic compoundcontaining a single carbon-carbon double bond, at least one aromaticmoiety, and a total of 8 to 18 carbon atoms, such as 8 to 12 carbonatoms. Exemplary monovinylarenes can include, but are not limited to,styrene, alpha-methylstyrene, 2-methylstyrene, 3-methylstyrene,4-methylstyrene, 2-ethylstyrene, 3-ethylstyrene, 4-ethylstyrene,4-n-propylstyrene, 4-t-butylstyrene, 2,4-dimethylstyrene,4-cyclohexylstyrene, 4-decylstyrene, 2-ethyl-4-benzylstyrene,4-(4-phenyl-n-butyl)styrene, 1-vinylnaphthalene, 2-vinylnaphthalene, andmixtures thereof. For example, in some embodiments disclosed herein, themonovinylarene can be styrene. A unit of a polymer, wherein the unit isderived from polymerization of a monovinylarene monomer, is a“monovinylarene unit.”

A “conjugated diene monovinylarene block copolymer” is a polymercomprising monovinylarene units and conjugated diene units. The polymercomprises one or more blocks, wherein each block comprisesmonovinylarene units and/or conjugated diene units. Any particular blockcan comprise either or both monovinylarene units or conjugated dieneunits. If it comprises only one type of unit, it can be termed a“monoblock,” If it comprises both, it can be termed a mixed block.Exemplary mixed blocks can include, but are not limited to, randomblocks, tapered blocks, stepwise blocks, or any other type of mixedblock.

A mixed block is “tapered” when both (a) the mole fraction of conjugateddiene units in a first section of the block is higher than the molefraction of conjugated diene units in a second section of the block,wherein the second section of the block is closer to a given end of theblock, and (b) condition (a) is true for substantially all sections ofthe block. Depending on the size of the sections being considered,condition (a) may not be true for all sections, but if so, will be nottrue at no more than about the level expected by chance.

A mixed block is “random” when the mole fractions of conjugated dieneunits and monovinylarene units in a section of the block aresubstantially the same as the mole fractions of conjugated diene unitsand monovinylarene units in the entire block. This does not preclude thepossibility of sections of the block having regularity (i.e., appearingnon-random), but such regular sections will typically be present at nomore than about the level expected by chance.

Although any methods and materials similar or equivalent to thosedescribed herein can be used in the practice or testing of theinvention, the typical methods and materials are herein described.

All publications and patents mentioned herein are incorporated herein,in their entirety, by reference for the purpose of describing anddisclosing, for example, the constructs and methodologies that aredescribed in the publications, which might be used in connection withthe presently described invention. The publications discussed throughoutthe text are provided solely for their disclosure prior to the filingdate of the present application. Nothing herein is to be construed as anadmission that the inventors are not entitled to antedate suchdisclosure by virtue of prior invention.

Applicants disclose several types of ranges in the present invention.When Applicants disclose or claim a range of any type, Applicants'intent is to disclose or claim individually each possible number thatsuch a range could reasonably encompass, including end points of therange as well as any sub-ranges and combinations of sub-rangesencompassed therein. A representative example follows for the MD:CDshrink ratio of a multilayer blown film in an embodiment of thisinvention. For example, by a disclosure that the multilayer blown filmhas a MD:CD shrink ratio in a range from about 4:1 to about 30:1,Applicants intend to recite that the ratio can be about 4:1, about 5:1,about 6:1, about 7:1, about 8:1, about 9:1, about 10:1, about 11:1,about 12:1, about 13:1, about 14:1, about 15:1, about 16:1, about 17:1,about 18:1, about 19:1, about 20:1, about 21:1, about 22:1, about 23:1,about 24:1, about 25:1, about 26:1, about 27:1, about 28:1, about 29:1,or about 30:1. Additionally, the MD:CD shrink ratio can be within anyrange from about 4:1 to about 30:1 (for example, the ratio is in a rangefrom about 12:1 to about 20:1), and this also includes any combinationof ranges between about 4:1 and about 30:1. Likewise, all other rangesdisclosed herein should be interpreted in a manner similar to thisrepresentative example.

Applicants reserve the right to proviso out or exclude any individualmembers of any such group, including any sub-ranges or combinations ofsub-ranges within the group, that can be claimed according to a range orin any similar manner, if for any reason Applicants choose to claim lessthan the full measure of the disclosure, for example, to account for areference that Applicants may be unaware of at the time of the filing ofthe application. Further, Applicants reserve the right to proviso out orexclude any individual substituents, analogs, compounds, ligands,structures, or groups thereof, or any members of a claimed group, if forany reason Applicants choose to claim less than the full measure of thedisclosure, for example, to account for a reference that Applicants maybe unaware of at the time of the filing of the application.

As used herein, “MD” refers to machine direction, and “CD” refers tocross direction. The cross direction also can be referred to herein asthe transverse direction (TD).

Various physical properties of multilayer blown films, as well as of thepolymeric components that are used to form these films, are discussedthroughout this disclosure. Following is a listing of physicalproperties and their corresponding analytical test procedures andconditions:

-   -   Melt index (MI), ASTM D1238 Revision Feb. 1, 2010, g/10 min,        190° C., 2.16 Kg weight.    -   High Load Melt Index (HLMI), ASTM D1238 Revision Feb. 1, 2010,        g/10 min, 190° C., 21.6 Kg weight.    -   Melt Flow Rate (MFR), ASTM D1238 Revision Feb. 1, 2010, g/10        min, 200° C., 5 Kg weight.    -   Density, ethylene polymers, ASTM D1505 Revision Jul. 1, 2010,        g/cm³.    -   Density, styrenic polymers, ASTM D792 Revision Jun. 15, 2008,        g/cm³.    -   Shrink, oil bath, ASTM D2732 Revision Nov. 1, 2008, %, 150° C.    -   Shrink tension, ASTM D2838 Revision May 1, 2009, Pa, 150° C.    -   Haze, ASTM D1003 Revision Nov. 1, 2007, %.    -   60° Gloss, ASTM D523 Revision Jun. 1, 2008, %.    -   1% Secant Modulus, ASTM D882 Revision Apr. 1, 2010, psi.    -   Tensile Strength at Break, ASTM D882 Revision Apr. 1, 2010, psi.    -   Vicat Softening Point, ASTM D1525 Revision Nov. 15, 2009, ° C.    -   Dart Impact, ASTM D1709 Revision May 1, 2009, g, 26 inch drop        height, varying dart weight to break.

DETAILED DESCRIPTION OF THE INVENTION

The present disclosure provides for multilayer blown films comprisingthree or more layers, and these films can have a MD shrink of greaterthan about 60% and a CD shrink in a range from 0% to about 15%. Suchshrink characteristics can be achieved using a standard blown filmprocess, without the added expense and complexity of orientationprocesses such as tenter frame, double bubble, machine directionorientation (MDO), and the like.

Multilayer Blown Films

Embodiments of this invention are directed to multilayer blown filmscomprising (a) a core layer having a first side and a second side; (b)an inner layer positioned on the first side of the core layer; and (c)an outer layer positioned on the second side of the core layer. In someembodiments, the multilayer blown film can have the three layers asdescribed generally as an inner layer, a core layer, and an outer layer,while in other embodiments, the multilayer blown film can have four ormore layers. Thus, the core layer is not limited only to a middle layerin between an inner layer and the outer layer, i.e., other layers can bepresent. The inner layer and the outer layer are described as beingpositioned on a first and a second side, respectively, of the corelayer. An additional layer, or layers, can be between the core layer andthe inner layer, and likewise, between the core layer and the outerlayer.

Various combinations of layers can be employed in the formation of themultilayer blown films in accordance with embodiments of this invention.FIGS. 1-4, respectively, illustrate representative 3-layer, 4-layer,5-layer, and 7-layer blown film structures. These and other non-limitinglayer configurations follow below, in which letters are used torepresent the film layers: I/C/O, I/M/C/O, I/C/M/O, I/M/M/C/O,I/M/C/M/O, I/C/M/M/O, I/M/M/C/M/O, I/M/C/M/M/O, I/M/M/M/C/O,I/M/M/C/M/M/O, I/M/M/M/C/M/O, and I/M/C/M/M/M/O. In these examples, “C”represents a core layer, “I” represents an inner layer, “O” representsan outer layer, and “M” represents a miscellaneous or intermediatelayer. Layers which are next to each other are described as beingaffixed to or adjacent to each other. For instance, in the multilayerstructure I/M/C/O, the “O” layer is adjacent to or affixed to the secondside of the “C” layer, and the “O” layer is also positioned on thesecond side of the “C” layer. Likewise, the “I” layer is not adjacent tonor affixed to the first side of the “C” layer, but is positioned on thefirst side of the “C” layer. Hence, by referring to a given layer aspositioned on a side of the core layer, the given layer can be adjacentto or affixed to the core layer, or an additional layer or layers (forexample, “M”) can be between the given layer and the core layer. Thereis no upper limit on the total number of layers in a multilayer blownfilm in accordance with this invention, for instance, 7-layer and9-layer structures, provided that the inner layer, core layer, and outerlayer are present within the multilayer blown film structure. Materialswhich can be used in the inner layer, core layer, outer layer, andmiscellaneous layer(s) are described herein below, and may be utilizedin any combination without limitation to further describe the multilayerblown film structure.

FIG. 1 illustrates a 3-layer blown film with an I/C/O layerconfiguration. Specifically, in this multilayer blown film, the innerlayer is adjacent the first side of the core layer, and the outer layeris adjacent the second side of the core layer. As described above andillustrated in FIGS. 2-4, multilayer blown films contemplated herein canhave four or more layers, e.g., the multilayer blown film can have fivelayers or seven layers. Accordingly, a miscellaneous or intermediatelayer (or layers) can be between the inner layer and the core layerand/or between the outer layer and the core layer.

Multilayer blown films described herein are not limited to anyparticular film thickness range, however, multilayer blown films usefulin many end-use applications generally have an average film thickness ina range from about 0.5 mils to about 10 mils, wherein a mil is equal to1/1000 of an inch, or 0.025 mm. In certain embodiments, the average filmthickness can be in a range from about 0.5 to about 5 mils, from about0.75 to about 4 mils, from about 1 to about 3 mils, or from about 1 toabout 2 mils. The core layer of the multilayer blown film can comprise,on average, from about 40% to about 85% of the total film thickness insome embodiments, while the core layer can comprise, on average, fromabout 50% to about 85%, or from about 60% to about 80%, of the totalfilm thickness in other embodiments. Likewise, the outer layer and theinner layer of the multilayer blown film, independently, can comprise,on average, from about 8% to about 25% of the total film thickness;alternatively, from about 10% to about 25%; or alternatively, from about10% to about 20%. Totals of these layer percentages of the inner layer,core layer, and outer layer do not exceed 100%, but in instances wherethe total is less than 100%, the remaining thickness can come from oneor more miscellaneous layers, which can comprise the same or differentpolymer (or same or different blend of polymers). For example, anillustrative multilayer blown film can have a 70% core layer, a 15%inner layer, and a 15% outer layer. As another example, an illustrativemultilayer blown film can have a 60% core layer, a 10% inner layer, a15% outer layer, and a 15% miscellaneous layer between the inner layerand the core layer.

Multilayer blown films in accordance with the present invention can havea beneficial combination of MD and CD shrink properties, For instance,in one embodiment, the MD:CD shrink ratio of the multilayer blown filmat 150° C. can be in a range from about 4:1 to about 100:1, from about4:1 to about 50:1, or from about 4:1 to about 30:1. In anotherembodiment, the muitilayer blown film can be characterized as having aMD:CD shrink ratio in a range from about 5:1 to about 30:1, from about8:1 to about 26:1, from about 10:1 to about 25:1, from about 12:1 toabout 20:1, or from about 14:1 to about 18:1.

Additionally or alternatively, the MD shrink of the multilayer blownfilm can be greater than about 60% and/or the CD shrink of themultilayer blown film can be in a range from 0% to about 15%. Applicantscontemplate that the MD shrink can be greater than about 65%, or greaterthan about 70%, in one embodiment, while in another embodiment, the MDshrink can be in a range from about 60% to about 95%, from about 65% toabout 90%, from about 70% to about 85%, or from about 75% to about 85%.Typical ranges for the CD shrink of the multilayer blown film caninclude, but are not limited to, from about 1% to about 15%, from about1 to about 12%, from 0% to about 10%, from about 1% to about 10% fromabout 2% to about 8%, from about 2% to about 4%, or from about 1% toabout 5%.

Generally, the multilayer blown film can have a MD and/or CD shrinktension at 150° C. in a range from about 50,000 to about 300,000 Pa. Forexample, the MD shrink tension can be in a range from about 75,000 toabout 275,000 Pa, from about 100,000 Pa to about 275,000 Pa, or fromabout 125,000 Pa to about 250,000 Pa. Similarly, the CD shrink tensioncan be in a range from about 50,000 to about 250,000 Pa, from about50,000 Pa to about 200,000 Pa, or from about 60,000 Pa to about 150,000Pa.

Multilayer blown films described herein can have optical properties,such as low haze and high gloss, which can provide beneficial aestheticor visual impact properties in certain end-use applications. In anembodiment, the haze of the multilayer blown film can be less than about10%; alternatively, less than about 8%; alternatively, less than about6%; alternatively, in a range from about 0.5% to about 8%;alternatively, in a range from about 0.5% to about 5%; or alternatively,in a range from about 1% to about 3%. Additionally or alternatively, themultilayer blown film can have a 60° gloss of greater than about 100%;alternatively, greater than about 125%; or alternatively, greater thanabout 140%.

Secant modulus often can be used as a measurement of the relativestiffness of a film, and in some end-use applications, it can bebeneficial for the film to have greater stiffness, e.g., a higher secantmodulus, to give the film a stiff or crisp feel. Multilayer blown filmsdescribed herein generally can have a MD and/or CD 1% secant modulus ofgreater than about 50,000 psi. For example, the MD and/or CD 1% secantmodulus can be greater than about 55,000 psi, greater than about 60,000psi, in range from about 50,000 psi to about 200,000 psi, or in a rangefrom about 50,000 psi to about 150,000 psi.

Multilayer blown films disclosed herein can have one or more of thevarious film thickness, layer configuration, layer ratio, MD shrink, CDshrink, shrink tension, haze, gloss, and/or 1% secant modulus propertiesas disclosed above. Moreover, in one embodiment, the multilayer blownfilm can comprise (a) a core layer having a first side and a secondside, the core layer comprising an ethylene polymer; (b) an inner layerpositioned on the first side of the core layer, the inner layercomprising a first stryene/butadiene copolymer; and (c) outer layerpositioned on the second side of the core layer, the outer layercomprising a second styrene/butadiene copolymer. In this embodiment, thefirst styrene/butadiene copolymer and the second styrene/butadienecopolymer can comprise the same polymer or the same blend of polymers,or alternatively, the first stryene/butadiene copolymer and the secondstryene/butadiene copolymer can comprise different polymers or adifferent blend of polymers. In another embodiment, the multilayer blownfilm can comprise (a) a core layer having a first side and a secondside, the core layer comprising an ethylene polymer; (b) inner layerpositioned on the first side of the core layer, the inner layercomprising a first conjugated diene monovinylarene block copolymer; and(c) an outer layer positioned on the second side of the core layer, theouter layer comprising a second conjugated diene monovinylarene blockcopolymer. In this embodiment, the first conjugated diene monovinylareneblock copolymer and the second conjugated diene monovinylarene blockcopolymer can comprise the same polymer or the same blend of polymers,or alternatively, the first conjugated diene monovinylarene blockcopolymer and the second conjugated diene monovinylarene block copolymercan comprise different polymers or a different blend of polymers. In yetanother embodiment, the multilayer blown film can comprise (a) a corelayer having a first side and a second side, the core layer comprisingan ethylene polymer; (b) an inner layer positioned on the first side ofthe core layer, the inner layer comprising a first coupled multimodalconjugated diene monovinylarene block copolymer; and (c) an outer layerpositioned on the second side of the core layer, the outer layercomprising a second coupled multimodal conjugated diene monovinylareneblock copolymer. In this embodiment, the first coupled multimodalconjugated diene monovinylarene block copolymer and the second coupledmultimodal conjugated diene monovinylarene block copolymer can comprisethe same polymer or the same blend of polymers, or alternatively, thefirst coupled multimodal conjugated diene monovinylarene block copolymerand the second coupled multimodal conjugated diene monovinylarene blockcopolymer can comprise different polymers or a different blend ofpolymers.

Core Layer

In an embodiment of this invention, a multilayer blown film can comprise(a) a core layer having a first side and a second side; (b) an innerlayer positioned on the first side of the core layer; and (c) an outerlayer positioned on the second side of the core layer, wherein themultilayer blown film has a MD:CD shrink ratio in a range of from about4:1 to about 30:1, and/or a MD shrink of greater than about 60%, and/ora CD shrink in a range from 0% to about 15%. Additionally oralternatively, a multilayer blown film can comprise (a) a core layerhaving a first side and a second side, the core layer comprising anethylene polymer; (b) an inner layer positioned on the first side of thecore layer, the inner layer comprising a first conjugated dienemonovinylarene block copolymer (or a first coupled multimodal conjugateddiene monovinylarene block copolymer, or a first stryene/butadienecopolymer, etc.); and (c) an outer layer positioned on the second sideof the core layer, the outer layer comprising a second conjugated dienemonovinylarene block copolymer (or a second coupled multimodalconjugated diene monovinylarene block copolymer, or a secondstryene/butadiene copolymer, etc.).

In one embodiment, the ethylene polymer can comprise a very low densitypolyethylene (VLDPE), a linear low density polyethylene (LLDPE), a lowdensity linear polyethylene (LDLPE), a high density polyethylene (HDPE),or a low density polyethylene (LDPE), and this can include any blend orcombination thereof. Accordingly, blends or combinations of more thanone ethylene polymer, as well as blends or combinations of an ethylenepolymer with another polymer, can be employed. In another embodiment,the ethylene polymer can comprise a very low density polyethylene(VLDPE), a linear low density polyethylene (LLDPE), a low density linearpolyethylene (LDLPE), or a high density polyethylene (HDPE), includingblends or combinations thereof. In yet another embodiment, the ethylenepolymer can comprise a very low density polyethylene (VLDPE);alternatively, a linear low density polyethylene (LLDPE); alternatively,a low density linear polyethylene (LDLPE); or alternatively, a highdensity polyethylene (HDPE). In these and other embodiments, the corelayer can further comprise another polymer including, but not limitedto, a polypropylene homopolymer, a polypropylene random copolymer, animpact polypropylene, an ethylene vinyl acetate copolymer, or anethylene acrylic acid copolymer, and the like, and includingcombinations thereof.

Suitable ethylene polymers are not limited to any particularpolymerization process and reactor system and/or any particular catalystsystem. For example, the polymerization reactor system used to producethe ethylene polymer can comprise a slurry reactor, a gas-phase reactor,a solution reactor, or various combinations thereof (e.g., includingdual reactor systems). The catalyst system used to produce the ethylenepolymer can be a chromium-based catalyst system, a Ziegler-Natta basedcatalyst system, a metallocene-based catalyst system, or combinationsthereof, and the catalyst system can comprise one or more transitionmetals, such as chromium, vanadium, titanium, zirconium, hafnium, andthe like, or combinations thereof. Hence, all traditional LLDPE polymersare encompassed herein, as well as all metallocene-catalyzed LLDPE(mLLDPE) resins.

Generally, HDPE resins have a density range of greater than about 0.945g/cm³, and VLDPE resins of below about 0.915 g/cm³, with LLDPE spanningbetween, although there can be, and often is, overlap. A LDLPE resin canbe described as a LLDPE resin with generally broader molecular weightdistribution, greater melt strength, and better bubble stability thaneither conventional LLDPE or mLLDPE. Moreover, the LDLPE often can havea fractional melt index, e.g., less than 1. While not being limitedthereto, certain suitable LDLPE polymers that can be employed in thecore layer of a multilayer blown film are described in U.S. Pat. Nos.4,735,931, 4,820,785, 4,966,951, 5,115,068, and 5,208,309, thedisclosures of which are incorporated herein by reference in theirentirety. Illustrative examples of LDLPE polymers can include, but arenot limited to, MarFlex® TR-257 and MarFlex® TR-258 polyethylenes,available from Chevron Phillips Chemical Company LP.

In some embodiments, the ethylene polymer can be an ethylenehomopolymer, while in other embodiments, the ethylene polymer can be anethylene copolymer or terpolymer. In the latter case, suitablecomonomers can include, but are not limited to, propylene, 1-butene.2-butene, 3-methyl-1-butene, isobutylene, 1-pentene, 2-pentene,3-methyl-1-pentene, 4-methyl-1-pentene, 1-hexene, 2-hexene,3-ethyl-1-hexene, 1-heptene, 2-heptene, 3-heptene, 1-octene, 1-decene,and the like, or combinations thereof. Often, the comonomer can comprisean α-olefin, such as 1-butene, 1-hexene, 1-octene, or a combinationthereof.

Ethylene polymers that can be employed in the core layer of themultilayer blown films disclosed herein generally can have a melt index(MI) in a range from about 0.01 to about 2 g/10 min. Melt indices in therange from about 0.02 to about 1.5 g/10 min, from about 0.05 to about 1g/10 min, or from about 0.07 to about 0.8 g/10 min, are contemplated insome embodiments of this invention. For example, an ethylene polymeruseful in the present invention can have a MI in the range from about0.09 to about 0.6 g/10 min, from about 0.1 to about 0.5 g/10 min, orfrom about 0.1 to about 0.3 g/10 min.

The ratio of HLMI/MI is often referred to as a melt flow ratio. Anethylene polymer used herein often can have a HLMI/MI ratio in a rangefrom about 50 to about 300, such as, for instance, from about 50 toabout 200, from about 50 to about 150, from about 60 to about 140, fromabout 70 to about 130, from about 70 to about 120, or from about 75 toabout 110.

An ethylene polymer within the scope of the present invention generallycan have a weight-average molecular weight (Mw) in a range from about75,000 to about 500,000 g/mol. In some embodiments, the Mw of theethylene polymer can be in range from about 90,000 to about 350,000g/mol, while in other embodiments, the Mw of the ethylene polymer can bein a range from about 100,000 to about 250,000 g/mol, from about 110,000to about 210,000 g/mol, or from about 120,000 to about 200,000 g/mol.Molecular weights and molecular weight distributions for the ethylenepolymers disclosed herein can be obtained using a PL 220 SEC hightemperature chromatography unit (Polymer Laboratories) withtrichlorobenzene (TCB) as the solvent, with a flow rate of 1 mL/minuteat a temperature of 145° C. BHT (6-di-tert-butyl-4-methylphenol) at aconcentration of 0.5 g/L can be used as a stabilizer in the TCB. Aninjection volume of 200 μL can be used with a nominal polymerconcentration of 1.5 mg/mL. Dissolution of the sample in stabilized TCBcan be carried out by heating at 150° C. for 5 hours with occasional,gentle agitation. The columns used can be three PLgel Mixed A LS columns(7.8×300 mm) and can be calibrated with a broad linear polyethylenestandard (Phillips Marlex® BHB 5003) for which the molecular weight hasbeen determined.

The ratio of Mw/Mn (weight-average to number-average molecular weightratio, or polydispersity index, or heterogeneity index) for the ethylenepolymers disclosed herein often can be in a range from about 3 to about50. In some embodiments, the Mw/Mn ratio can be in a range from about 4to about 40. Specifically contemplated ranges for the ratio of Mw/Mnencompassed by the present invention can include, but are not limitedto, from about 5 to about 30, from about 5 to about 25, from about 5 toabout 20, from about 6 to about 20, from about 6 to about 18, from about6 to about 16, from about 6 to about 13, from about 8 to about 16, fromabout 7 to about 15, from about 9 to about 15, from about 7 to about 13,from about 8 to about 14, or from 9 to about 13.

In an embodiment, the density of the ethylene polymer typically can fallwithin the range from about 0.88 to about 0.96 g/cm³, or from about 0.88to about 0.94 g/cm³. In another embodiment, the ethylene polymer densitycan be in a range from about 0.895 to about 0.93 g/cm³, or from about0.90 to about 0.93 g/cm³. Yet, in another embodiment, the density can bein a range from about 0.915 to about 0.935 g/cm³, from about 0.919 toabout 0.935 g/cm³, from about 0.92 to about 0.929 g/cm³, or from about0.921 to about 0.925 g/cm³.

Inner and Outer Layers

In an embodiment of this invention, a multilayer blown film can comprise(a) a core layer having a first side and a second side; (b) an innerlayer positioned on the first side of the core layer; and (c) an outerlayer positioned on the second side of the core layer, wherein themultilayer blown film has a MD:CD shrink ratio in a range of from about4:1 to about 30:1, and/or a MD shrink of greater than about 60%, and/ora CD shrink in a range from 0% to about 15%. Additionally oralternatively, the multilayer blown film can comprise (a) a core layerhaving a first side and a second side, the core layer comprising anethylene polymer; (b) an inner layer positioned on the first side of thecore layer, the inner layer comprising a first conjugated dienemonovinylarene block copolymer (or a first coupled multimodal conjugateddiene monovinylarene block copolymer, or a first stryene/butadienecopolymer, etc.); and (c) an outer layer positioned on the second sideof the core layer, the outer layer comprising a second conjugated dienemonovinylarene block copolymer (or a second coupled multimodalconjugated diene monovinylarene block copolymer, or a secondstryene/butadiene copolymer, etc.). In these and other embodiments, theinner layer and the outer layer can comprise the same polymer or thesame blend of polymers (e.g., the first conjugated diene monovinylareneblock copolymer and the second conjugated diene monovinylarene blockcopolymer can be the same), or alternatively, the inner layer and theouter layer can comprise different polymers or a different blend ofpolymers (e.g., the first conjugated diene monovinylarene blockcopolymer and the second conjugated diene monovinylarene block copolymercan be different). In further embodiments, the inner layer and/or theouter layer can provide a surface capable of surface printing and/orreverse printing, a surface providing good printability, a surface withadequate surface energy (e.g., dyne level) retention for variousprinting ink types/systems, etc.

While not being limited thereto, certain suitable conjugated dienemonovinylarene block copolymers that can be employed in the inner layerand/or the outer layer of a multilayer blown film are described in U.S.Pat. Nos. 6,096,828, 6,420,486, 6,444,755, 6,835,778, 7,037,980, and7,193,014, the disclosures of which are incorporated herein by referencein their entirety; and U.S. Patent Publication Nos. 2006/0089457,2007/0173605, and 2008/0134642, the disclosures of which areincorporated herein by reference in their entirety. Illustrativeexamples of conjugated diene monovinylarene block copolymers caninclude, but are not limited to, K-Resin® SEC, available from ChevronPhillips Chemical Company LP, and grades such as, for instance, DK11,KR52, or KR53, all available from Chevron Phillips Chemical Company LP

The relative amount of conjugated diene and monovinylarene in a blockcopolymer can vary broadly depending on the particular characteristicsdesired. Generally, the conjugated diene/monovinylarene block copolymercan contain monovinylarene monomer in an amount in the range of fromabout 55 weight percent to about 95 weight percent, based on the totalweight of the final block copolymer; alternatively, in the range of fromabout 60 weight percent to about 95 weight percent; or alternatively, inthe range of from 65 weight percent to 90 weight percent.

Likewise, the conjugated diene monomer can be present in the final blockcopolymer in an amount in the range of from about 45 weight percent toabout 5 weight percent, based on the total weight of the final blockcopolymer; alternatively, in the range of from about 40 weight percentto about 5 weight percent; or alternatively, in the range of from about35 weight percent to about 10 weight percent.

In one embodiment of the present invention, the inner layer and/or theouter layer independently can comprise a conjugated diene monovinylareneblock copolymer, while in another embodiment, the inner layer and/or theouter layer independently can comprise a coupled conjugated dienemonovinylarene block copolymer, and in yet another embodiment, the innerlayer and/or the outer layer independently can comprise a coupledmultimodal conjugated diene monovinylarene block copolymer, in these andother embodiments contemplated herein, the block copolymer can comprisemixed conjugated diene/monovinylarene blocks selected from randomblocks, tapered blocks, or combinations thereof. In another embodiment,the block copolymer can comprise at least three consecutive conjugateddiene/monovinylarene mixed blocks. In an embodiment, the block copolymercan comprise at least three consecutive tapered blocks. In anembodiment, the block copolymer can comprise at least three consecutiverandom blocks. In yet another embodiment, the block copolymer cancomprise at least four blocks of conjugated diene, monovinylarene, ormixed conjugated diene/monovinylarene blocks. In yet another embodiment,the block copolymer can comprise at least five blocks of conjugateddiene, monovinylarene, or mixed conjugated diene/monovinylarene blocks.And, in still another embodiment, the block copolymer can comprise fromabout 55 weight percent to about 90 weight percent monovinylareneresidues; alternatively, from about 65 weight percent to about 85 weightpercent; or alternatively, from about 71 weight percent to about 79weight percent. In these and other embodiments, the monovinylarene cancontain from 8 to 18 carbon atoms (e.g., styrene), and the conjugateddiene can contain from 4 to 12 carbon atoms (e.g., butadiene).

In accordance with some embodiments of this invention, the blockcopolymer can be produced by coupling at least two different livingpolymer chains having been produced by at least two separate charges ofinitiator. In other embodiments, the block copolymer can comprise aplurality of mixed conjugated diene/monovinylarene blocks, wherein eachmixed conjugated diene/monovinylarene block can contain conjugated dieneunits and monovinylarene units with a weight ratio of conjugated dieneunits to monovinylarene units in a range from about 0.05 to about 0.33,from about 0.6 to about 0.28, or from about 0.08 to about 0.26.

The inner layer and/or outer layer of the multilayer blown filmindependently can comprise a block copolymer, as described above, but isnot limited thereto. For instance, blends of various polymers can bemade with the block copolymer. Therefore, the inner layer and/or theouter layer independently can further comprise a general purposepolystyrene, a high impact polystyrene, acyclic olefin copolymer, astyrene isoprene styrene copolymer, or a styrene ethylene-butylenestyrene polymer, as well as blends or combinations thereof. Weightpercentages of the additional polymer(s) can be, for example, up toabout 10%, up to about 20%, up to about 30%, up to about 40%, up toabout 50%, or up to about 60%, based on the total weight of inner layerand/or outer layer. In an embodiment, the inner layer and/or the outerlayer independently can comprise a block copolymer (e.g., a conjugateddiene monovinylarene block copolytner) and a general purposepolystyrene; alternatively, a conjugated diene monovinylarene blockcopolymer and a high impact polystyrene; alternatively, a conjugateddiene monovinylarene block copolymer and a cyclic olefin copolymer(e.g., an ethylene-norbornene copolymer); alternatively, a conjugateddiene monovinylarene block copolymer and a styrene isoprene styrenecopolymer; or alternatively, a conjugated diene monovinylarene blockcopolymer and a styrene ethylene-butylene styrene polymer.

In some embodiments, the inner layer and/or the outer layerindependently can comprise a K-Resin® SBC, available from ChevronPhillips Chemical Company LP, such as, for instance, DK11 (7.5 g/10 minMFR), KR52 (9 g/10 min MFR), or KR53 (10 g/10 min MFR), and the like, orany combination thereof. Accordingly, the inner layer and/or the outerlayer independently can comprise DK11; alternatively, can comprise KR52;or alternatively, can comprise KR53. And, such inner layer and/or outerlayer independently can further comprise a general purpose polystyrene,a high impact polystyrene, a cyclic olefin copolymer, a styrene isoprenestyrene copolymer, or a styrene ethylene-butylene styrene polymer, andincluding blends or combinations thereof.

Block copolymers that can be employed in the inner layer and/or theouter layer of the multilayer blown films disclosed herein generally canhave a melt flow rate (MFR) in a range from about 0.5 to about 30 g/10min. MFR's in the range from about 1 to about 25 g/10 min, from about 1to about 20 g/10 min, or from about 2 to about 18 g/10 min, arecontemplated in some embodiments of this invention. For example, a blockcopolymer useful in the present invention can have a melt flow rate in arange from about 2 to about 15 g/10 min, from about 3 to about 15 g/10min, or from about 5 to about 14 g/10 min.

Miscellaneous or Intermediate Layers

In some embodiments of this invention, the multilayer blown film cancomprise a miscellaneous or intermediate layer. Any miscellaneous orintermediate layer (one, or more than one) that may be present in themultilayer blown film can comprise any of the polymers discussed aboveas being polymer options for the core layer, inner layer, and/or outerlayer. Additional polymers that can be employed either singly or incombination in the miscellaneous or intermediate layer can include, butare not limited to, a polypropylene homopolymer, a polypropylene randomcopolymer, an impact polypropylene, an ethylene vinyl acetate copolymer(EVA), or an ethylene acrylic acid copolymer (EAA), and the like, orcombinations thereof.

Moreover, in one embodiment, the miscellaneous or intermediate layer canbe a tie layer, while in another embodiment, the miscellaneous orintermediate layer can be a layer comprising regrind. A tie layer can beused to promote adhesion between the inner layer and the core layerand/or between the outer layer and the core layer. Optionally, in someembodiments, a tie layer can be used, for example, comprising an EVA,typically with a vinyl acetate content over 6-9% by weight, orcomprising an EAA, typically with an acrylic acid content of over 6-9%by weight.

In other embodiments, however, the multilayer blown film structure doesnot contain a tie layer between the inner layer and the core layer orbetween the outer layer and the core layer. In this embodiment, theinterlayer bond strengths between the inner layer and the core layer andbetween the outer layer and the core layer are acceptable for theend-use application, and the addition of a tie layer merely adds costand complexity.

Additives

Additives are often used in polymer films and formulations to improvethe processing or ease of manufacturing of the polymer(s) and itsintended finished article. Another use of additives is to impart acertain property or characteristic to the finished article. Inembodiments of the present invention, one or more additives can beemployed in the inner layer, and/or the outer layer, and/or the corelayer, and/or any of the miscellaneous or intermediate layers that maybe present. Suitable additives which can be employed in the blown filmstructures or formulations disclosed herein can include, but are notlimited to, antioxidants, acid scavengers, antiblock additives, slipadditives, colorants, fillers, polymer processing aids, UV inhibitors,and the like, including combinations thereof. Therefore, in certainembodiments, the multilayer blown film can comprise an additive selectedfrom an antioxidant, an acid scavenger, an antiblock additive, a slipadditive, a colorant, a tiller, a polymer processing aid, a UVinhibitor, and the like, or any combination thereof.

Processes for Producing Multilayer Blown Films

Processes for producing multilayer blown films also are disclosedherein. One such process can comprise:

(i) introducing into a blown film coextrusion die:

-   -   (a) a core layer flow having a first side and a second side,    -   (b) an inner layer flow positioned on the first side of the core        layer flow, and    -   (c) an outer layer flow positioned on the second side of the        core layer flow; and

(ii) blowing a coextruded flow exiting the die at a blow-up ratio in arange from about 1.5 to about 4 to produce the multilayer blown film.

In an embodiment, the resulting multilayer blown film can have a MD:CDshrink ratio in a range of from about 4:1 to about 30:1, and/or the MDshrink of the multilayer blown film can be greater than about 60%,and/or the CD shrink of the multilayer blown film can be in a range from0% to about 15%.

In another embodiment, the core layer flow can comprise an ethylenepolymer, e.g., any ethylene polymer described herein. Further, the innerlayer flow and the outer layer flow, independently, can comprise anystryene/butadiene copolymer disclosed herein, any conjugated dienemonovinylarene block copolymer disclosed herein, or any coupledmultimodal conjugated diene monovinylarene block copolymer disclosedherein, etc.

The multilayer, or coextruded, blown film can be produced using anytraditional blown film equipment (extruders, die, etc.), which are wellknown to those of skill in the art. Such is described, for example, inthe Modern Plastics Encyclopedia, Mid-November 1995 Issue, Vol. 72, No.12; and Film Extrusion Manual—Process, Materials, Properties, TAPPIPress, 1992; the disclosures of which are incorporated herein byreference in their entirety.

Additionally, the process for producing a multilayer blown filmdescribed herein does not include nor comprise a double-bubbleorientation step, and/or a machine direction orientation (MDO) step,and/or a tenter frame orientation step. These additional steps (and theassociated equipment) can add additional cost and complexity to the filmproduction process and, therefore, are not needed. Hence, in the presentinvention, no post-extrusion (blown film extrusion) orientation processsteps are necessary.

As the traditional blown film process applies to the multilayer blownfilms contemplated herein, the blow-up ratio employed generally can bein a range from about 1.5 to about 4. In another embodiment, the blow-upratio can be in the range from about 2 to about 3. In yet anotherembodiment, the blow-up ratio can be in the range from about 1.7 about3.5, In still another embodiment, the blow-up ratio can be in the rangefrom about 2 to about 2.8, or from about 2 to about 2.6.

Moreover, in some embodiments, the MD shrink can be generally unaffectedby the blow-up ratio, or alternatively, can decrease slightly as theblow-up ratio increases. In other embodiments, the CD shrink can beimpacted by and/or correlated with the blow-up ratio, e.g., the CDshrink can generally increase as the blow-up ratio increases.Accordingly, while not being bound by theory. Applicants believe thatthe CD shrink of a multilayer blown film can be adjusted and/orcontrolled by changing the blow-up ratio used to produce the multilayerblown film.

Articles of Manufacture

Multilayer blown films described herein can be used to produce variousarticles of manufacture. For instance, labels can be formed from and/orcan comprise a multilayer blown film in accordance with this invention.Illustrative and non-limiting labels can include shrink sleeve labels,roll fed shrink labels, and the like As an example, the multilayer blownfilm can be printed on the inner layer and/or on the outer layer usingvarious known processes (e.g., flexographic, rotogravure, etc.), andoptionally laminated to another film of the same or different type, toform a printed label.

In another embodiment, an article of manufacture encompassed herein cancomprise a container or a package and a label, the label comprising amultilayer blown film. In this regard, the container or the package canbe a bottle, a can, a canister, a tube, a cup, or a box, and the like,but is not limited thereto. The label can be applied or affixed to thecontainer or package using any suitable means known to those of skill inthe art (e.g., roll fed labeling machinery).

In yet another embodiment, an article of manufacture can comprise acontainer or a package and a label or a multilayer blown film. In thisregard, the container or the package can be a collection (or plurality)of bottles, cans, canisters, tubes, cups, or boxes, and the like, orcombinations thereof. In this application, the label or multilayer filmcan serve as a bundling wrap for the various collection or plurality ofitems.

EXAMPLES

The Invention is further illustrated by the following examples, whichare not to be construed in any way as imposing limitations to the scopeof this invention. Various other aspects, embodiments, modifications,and equivalents thereof which, after reading the description herein, maysuggest themselves to one of ordinary skill in the art without departingfrom the spirit of the present invention or the scope of the appendedclaims.

Examples 1-5

Property Comparison of 3-Layer Blown Films

Three-layer blown films were produced using standard coextrusion blownfilm equipment. The extruder for the core layer had a 3.5-inch diameterand a 30:1 length-to-diameter (L/D) ratio, and the extruder for theinner layer and outer layer had a 2-inch diameter and a 30:1 L/D ratio.Melt temperatures were approximately 400° F. The coextrusion die had an8-inch diameter and the die gap was 60 mils. The blow-up ratio (BUR) was2.5:1.

Films were produced at a nominal thickness of 1.5 mils. The core layerwas 70% of the total thickness, and the inner layer and the outer layerwere the same polymer composition, and each constituted about 15% of thetotal thickness. Table I summarizes the compositions of each of thelayers of the blown films of Examples 1-5. Table II compares theproperties of the blown films of Examples 1-5.

FIG. 5 and FIG. 6 are plots comparing the haze and the 60° gloss,respectfully, of the 3-layer blown films of Examples 1-5. Each of themultilayer blown films had haze values less than 4.5% and 60° glossvalues of over 140%. FIG. 7 is a plot comparing the 1% secant modulus inthe MD and CD for the 3-layer blown films of Examples 1-5. Generally,these films had modulus (MD and CD) values near or above 300 MPa (about43,500 psi). The film of Example 2 had modulus values (MD and CD) over450 MPa (about 65,000 psi).

FIG. 8 is a plot comparing the percentage shrink at 150° C. In the MDand CD for the 3-layer blown films of Examples 1-5. The film of Example2 demonstrated a unique and unexpected imbalance of MD and CD shrink,e.g., high MD shrink and low CD shrink. The MD shrink for the film ofExample 2 was about 80%, while the CD shrink was less than about 5%.

FIG. 9 is a plot comparing the tensile strength at break in the MD andCD for the 3-layer blown films of Examples 1-5. The film of Example 2had the highest MD tensile strength of these films. FIG. 10 is a plotcomparing the dart impact strength of the 3-layer blown films ofExamples 1-5. Each of these films had dart impact values of over 300 g.

TABLE I Blown Film Structures for Examples 1-5 Exam- ple Core LayerInner Layer and Outer Layer Blend 1 LLDPE 7109 97% SBC KR53 3% HIPS 7800MI - 0.9 g/10 min MFR - 10 g/10 min MFR - 3.6 g/10 min Density - 0.918Density - 1.01 Particle Size ~1.5 μm Vicat ~61° C. 2 LDLPE TR-257 97%SBC KR53 3% HIPS 7800 MI - 0.2 g/10 min MFR - 10 g/10 min MFR - 3.6 g/10min Density - 0.923 Density - 1.01 Particle Size ~1.5 μm Vicat ~61° C. 3mLLDPE D143 97% SBC KR53 3% HIPS 7800 MI - 1.4 g/10 min MFR - 10 g/10min MFR - 3.6 g/10 min Density - 0.916 Density - 1.01 Particle Size ~1.5μm Vicat ~61° C. 4 LDPE 5628 97% SBC KR53 3% HIPS 7800 MI - 0.4 g/10 minMFR - 10 g/10 min MFR - 3.6 g/10 min Density - 0.922 Density - 1.01Particle Size ~1.5 μm Vicat ~61° C. 5 99% SBC KR53 99% SBC KR53 1% HIPS7800 1% HIPS 7800 MFR - 10 g/10 min MFR - 3.6 g/10 min (same an innerDensity - 1.01 Particle Size ~1.5 μm and outer layers) Vicat ~61° C.Notes on Table I: The ethylene polymer resins are commercially availablefrom Chevron Phillips Chemical Company LP. K-Resin ® SBC KR53 iscommercially available from Chevron Phillips Chemical Company LP. HIPS7800 is commercially available from INEOS Styrenics, and was added toreduce film blocking. The particle size listed is for the elastomericcomponent present in the HIPS polymer.

TABLE II Property Summary for the Blown Film Structures of Examples 1-5Exam- Exam- Exam- Exam- Exam- ple ple ple ple ple 1 2 3 4 5 Elmendorfg/mil MD 64.2 81.5 143.7 163.4 75.3 Tear TD 39.4 242.7 48.7 143.2 101.6Tensile % MD 307% 282% 357% 117% 229% Elongation TD 460% 476% 444% 360%201% Tensile MPa MD 14.9 17.1 13.2 40.6 20.7 Yield TD 13.6 16.2 12.213.8 16.9 Tensile MPa MD 32.0 49.2 35.4 40.6 32.4 Break TD 28.0 27.534.2 21.5 21.9 Secant MPa MD 384 522 337 387 666 Modulus TD 367 477 278391 471 Haze %  4.1%  3.2%  2.5%  2.0%  0.2% Gloss - 60° % 148% 147%152% 151% 166% Dart g 428 402 500 348 538 Impact Shrinkage - % MD 68 8066 80 50 150° C. TD 19 5 22 23 25

Examples 6-9

Properly Comparison of 3-Layer Blown Films at Different Blow-Up Ratios(“BUR's”)

Three-layer blown films were produced using standard coextrusion blownfilm equipment. The extruder for the core layer had a 3.5-inch diameterand a 30:1 L/D ratio, and the extruder for the inner layer and outerlayer had a 2-inch diameter and a 30:1 L/D ratio. Melt temperatures wereapproximately 380° F. for the inner/outer layers and 400° F. for thecore layer. The coextrusion die had an 8-inch diameter and the die gapwas 60 mils. Examples 6-9 were produced at BUR's of 1.35:1, 2:1, 3:1,and 4:1, respectively.

Films were produced at a nominal thickness of 2 mils. The core layer was80% of the total thickness, and the inner layer and the outer layer werethe same polymer composition, and each constituted about 10% of thetotal thickness. The core layer was Marflex® TR-257 polyethylene. Theinner layer and the outer layer contained 98% KR52 K-Resin® SBC and 2%SKR17, both available from Chevron Phillips Chemical Company LP. TableIII compares the properties of the blown films of Examples 6-9. FIG. 11is a plot comparing the percentage shrink at 150° C. In the MD and CDfor the 3-layer blown films of Examples 6-9, at respective BUR's of1.35:1, 2:1, 3:1, and 4:1. FIG. 11 demonstrates that the CD shrinkincreases rapidly with increasing blow-up ratio for these blown films.

TABLE III Property Summary for the Blown Film Structures of Examples 6-9Elmendorf Shrink 1% Secant Dart Tear Shrinkage Tension Modulus Drop(g/mil) (%, @150° C.) (Pa, 150° C.) (PSI) Example BUR (g) MD CD MD CD MDCD MD CD 6 1.35 176 15.3 435.2 70 −21.7 209,257 78,482 121,200 123,465 72.00 260 27.9 320.2 68.3 0 222,241 92,530 118,609 115,387 8 3.00 44840.2 160.3 62.5 25 182,347 95,127 110,186 116,051 9 4.00 418 47.2 171.755 32.5 141,408 105,094 112,962 115,554

We claim:
 1. A process for producing a multilayer blown film, theprocess comprising: (i) introducing into a blown film coextrusion die:(a) a core layer flow having a first side and a second side, the corelayer flow comprising an ethylene polymer characterized by: a MI in arange from about 0.01 to about 2 g/10 min; a ratio of HLMI/MI in a rangefrom about 50 to about 300; and a ratio of Mw/Mn in a range from about 5to about 30; (b) an inner layer flow positioned on the first side of thecore layer flow, the inner layer flow comprising a first conjugateddiene monovinylarene block copolymer; and (c) an outer layer flowpositioned on the second side of the core layer flow, the outer layerflow comprising a second conjugated diene monovinylarene blockcopolymer; and (ii) blowing a coextruded flow exiting the die at ablow-up ratio in a range from about 1.5 to about 4 to produce themultilayer blown film; wherein the multilayer blown film has a MD shrinkgreater than about 60% and a CD shrink in a range from 0% to about 15%at 150° C.
 2. The process of claim 1, wherein the blow-up ratio is in arange from about 2 to about
 3. 3. The process of claim 1, wherein theprocess does not comprise a double-bubble orientation step, a machinedirection orientation step, or a tenter frame orientation step.
 4. Theprocess of claim 1, wherein the multilayer blown film has a MD shrink ina range from about 65% to about 90% and a CD shrink in a range fromabout 1% to about 10% at 150° C.
 5. The process of claim 1, wherein themultilayer blown film has a MD:CD shrink ratio in a range from about 4:1to about 30:1 at 150° C.
 6. The process of claim 1, wherein the ethylenepolymer is an ethylene/α-olefin copolymer.
 7. The process of claim 6,wherein the ethylene/α-olefin copolymer is characterized by: a MI in arange from about 0.1 to about 0.5 g/10 min; a ratio of HLMI/MI in arange from about 60 to about 140; a Mw in a range from about 75,000 toabout 500,000 g/mol; a ratio of Mw/Mn in a range from about 7 to about15; and a density in a range from about 0.88 to about 0.94 g/cm³.
 8. Theprocess of claim 1, wherein: the first conjugated diene monovinylareneblock copolymer has from about 55 to about 95 weight percentmonovinylarene monomer content, based on the total weight of the blockcopolymer; and the second conjugated diene monovinylarene blockcopolymer has from about 55 to about 95 weight percent monovinylarenemonomer content, based on the total weight of the block copolymer. 9.The process of claim 8, wherein: the first conjugated dienemonovinylarene block copolymer comprises a first styrene butadiene blockcopolymer; and the second conjugated diene monovinylarene blockcopolymer comprises a second styrene butadiene block copolymer.
 10. Theprocess of claim 1, wherein: the inner layer flow further comprises ageneral purpose polystyrene, a high impact polystyrene, a cyclic olefincopolymer, a styrene isoprene styrene copolymer, a styreneethylene-butylene styrene polymer, or any combination thereof; the outerlayer flow further comprises a general purpose polystyrene, a highimpact polystyrene, a cyclic olefin copolymer, a styrene isoprenestyrene copolymer, a styrene ethylene-butylene styrene polymer, or anycombination thereof; or both.
 11. The process of claim 1, wherein themultilayer blown film further comprises an additive selected from anantioxidant, an acid scavenger, an antiblock additive, a slip additive,a colorant, a filler, a polymer processing aid, a UV inhibitor, or anycombination thereof.
 12. The process of claim 1, wherein the inner layerflow and the outer layer flow comprise different polymers or blends ofpolymers.
 13. A process for producing a multilayer blown film, theprocess comprising: (i) introducing into a blown film coextrusion die:(a) a core layer flow having a first side and a second side, the corelayer flow comprising an ethylene polymer, wherein the ethylene polymeris an ethylene/1-butene, ethylene/1-hexene, or ethylene/1-octenecopolymer characterized by: a MI in a range from about 0.01 to about 2g/10 min; a ratio of HLMI/MI in a range from about 50 to about 300; anda ratio of Mw/Mn in a range from about 5 to about 30; (b) an inner layerflow positioned on the first side of the core layer flow, the innerlayer flow comprising a first conjugated diene monovinylarene blockcopolymer; and (c) an outer layer flow positioned on the second side ofthe core layer flow, the outer layer flow comprising a second conjugateddiene monovinylarene block copolymer; and (ii) blowing a coextruded flowexiting the die at a blow-up ratio in a range from about 1.5 to about 4to produce the multilayer blown film; wherein the multilayer blown filmhas a MD shrink greater than about 60% and a CD shrink in a range from0% to about 15% at 150° C.
 14. The process of claim 13, wherein themultilayer blown film has a MD:CD shrink ratio in a range from about 4:1to about 30:1 at 150° C.
 15. The process of claim 13, wherein theblow-up ratio is in a range from about 2 to about
 3. 16. The process ofclaim 13, wherein the process does not comprise a double-bubbleorientation step, a machine direction orientation step, or a tenterframe orientation step.
 17. The process of claim 13, wherein theethylene/1-butene, ethylene/1-hexene, or ethylene/1-octene copolymer ischaracterized by: a MI in a range from about 0.1 to about 0.5 g/10 min;a ratio of HLMI/MI in a range from about 60 to about 140; and a ratio ofMw/Mn in a range from about 7 to about
 15. 18. The process of claim 13,wherein the ethylene/1-butene, ethylene/1-hexene, or ethylene/1-octenecopolymer is characterized by: a MI in a range from about 0.1 to about0.5 g/10 min; a ratio of HLMI/MI in a range from about 60 to about 140;a Mw in a range from about 75,000 to about 500,000 g/mol; a ratio ofMw/Mn in a range from about 7 to about 15; and a density in a range fromabout 0.88 to about 0.94 g/cm³.
 19. The process of claim 13, wherein themultilayer blown film has: a MD shrink in a range from about 65% toabout 90%; a CD shrink in a range from 1% to about 10%; an average filmthickness in a range from about 0.5 to about 5 mils; a haze of less thanabout 10%; a 60° gloss of greater than about 100%; and a 1% MD secantmodulus greater than about 50,000 psi.
 20. The process of claim 13,wherein: the first conjugated diene monovinylarene block copolymer hasfrom about 55 to about 95 weight percent monovinylarene monomer content,based on the total weight of the block copolymer, and the firstconjugated diene monovinylarene block copolymer comprises a firststyrene butadiene block copolymer; and the second conjugated dienemonovinylarene block copolymer has from about 55 to about 95 weightpercent monovinylarene monomer content, based on the total weight of theblock copolymer, and the second conjugated diene monovinylarene blockcopolymer comprises a second styrene butadiene block copolymer.